1. Field of the Invention
The present invention relates to a ceramic compact having a buried conductor, a ceramic part, a method for producing a ceramic compact, and a method for producing a ceramic part. For example, the ceramic compact and the ceramic part can be used for forming a passive component part excellent in radio-frequency properties.
2. Description of the Related Art
A passive component part using a dielectric substrate can be produced such that a conductor pattern is printed on a green sheet containing a ceramic powder and a resin, and a plurality of such green sheets are stacked, integrated, shaped, and burned (see, for example, Japanese Patent Publication No. 40-019975 and Japanese Laid-Open Patent Publication No. 02-058816).
In this case, the conductor pattern formed on the green sheet has a convex shape, so that the portions surrounding the conductor pattern are not pressed in the process of stacking the green sheets. As a result, the green sheet may be peeled off, and an edge of the conductor pattern may be crushed, resulting in deterioration in the electrical properties of the conductor. Further, the thickness of the conductor pattern cannot be increased because of these problems, whereby the resistance value can be reduced and the radio-frequency properties can be improved only to a limited extent.
To solve the above problems, in a conventional method, a conductor paste is printed on a base or a green sheet such as a resin film, a slurry of a ceramic powder and a resin is applied thereto, and the resultant is immersed in a cationic coagulation bath to convert the slurry to a gel, whereby a conductor pattern is buried in the green sheet (see, for example, Japanese Patent Publication No. 40-019975, and Japanese Laid-Open Patent Publication Nos. 02-058816 and 2005-001279).
In another conventional method, a thermoplastic resin, a thermosetting resin, or an ultraviolet curing resin is added to a conductor paste, whereby deformation of a conductor pattern is prevented (see, for example, Japanese Laid-Open Patent Publication No. 08-167537).
In a further conventional method, a metal wire coil is placed in a casting mold, the casting mold is filled with a ceramic slurry such that the metal wire is enclosed by the ceramic slurry, and the resultant is dried to produce an electronic part having the metal wire coil enclosed in a ceramic compact (see, for example, Japanese Laid-Open Patent Publication No. 11-126724).
In the method proposed in Japanese Patent Publication No. 40-019975 and Japanese Laid-Open Patent Publication Nos. 02-058816 and 2005-001279, when the slurry contains the ceramic powder and a thermoplastic resin, and the conductor paste contains a thermoplastic resin, the slurry is greatly shrunk in the drying process. As a result, since the portions in the vicinity of the conductor may be cracked, the integration of the ceramic compact and the conductor is deteriorated, and the green sheet becomes uneven due to the convex shape of the conductor. Further, because the thermoplastic resin in the conductor paste is easily dissolved in a solvent, the conductor may be disadvantageously dissolved in the ceramic, and the patterned shape of the conductor may be deformed, when the ceramic compact is formed.
Furthermore, in the method of Japanese Laid-Open Patent Publication No. 2005-001279, a large number of processes are required to produce a multilayered conductor pattern stack because the layers have to be separately subjected to the processes of the formation of the conductor pattern on the green sheet, the application of the slurry, the immersion in the cationic coagulation bath, and the drying.
In the method of Japanese Laid-Open Patent Publication No. 08-167537, the conductor pattern is printed on the green sheet, and a plurality of such green sheets are stacked, integrated, and pressed. Therefore, the portions in the vicinity of the conductor pattern are not pressed, and the green sheet may be peeled from the stack, like the method of Japanese Patent Publication No. 40-019975 and Japanese Laid-Open Patent Publication No. 02-058816.
The method of Japanese Laid-Open Patent Publication No. 11-126724 is suitable for burying an element such as a resistor or a coil in the ceramic compact. However, the method cannot be used for forming a multilayer conductor pattern stack.